For many years, hazardous liquids have been used pervasively throughout industry - most notably in the areas of motor fuels, garment cleaning, aircraft manufacture and electronics manufacture. Environmental concerns have triggered a need for improved safeguards in the prevention of environmental release of hazardous liquids. City, county, and state governments have enacted legislation regulating the manner in which hazardous liquids are stored. Since it is common to locate storage tanks containing hazardous liquids below ground, and any storage tank has the potential to develop a breach wherein the product is able to escape the tank and be released into the environment, the product may reach and contaminate a water supply or cause many other hazardous situations. To minimize the release of hazardous liquids, certain government regulations require the use of a double wall storage tank.
The double wall tank has an inner wall and an outer wall. With a double wall tank, product is contained within the inner wall. Product that may pass through a breach in the inner wall would be held in the annular space between the inner and outer walls of the tank. Conversely, water from the neighboring soil that may pass through a breach in the outer wall would also enter the annular space. When either the outer wall or the inner wall is breached, the double wall storage tank must be replaced or repaired before product release into the environment occurs. In many areas, regulations require installation of a sensing device to indicate failure of either the outer wall or the inner wall.